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LMR16006: Output Ripple Increase with Additional Probe (8pF//1M-ohm)?

Ting Ye
Genius 11800 points

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    TI__Genius 11800 points

    It is tested on LMR16006X EVM~

  • 0 in reply to Ting Ye
    TI__Mastermind 25590 points

    Ting,

    The ripple does not actually increase when you place a scope probe on the SW node. What's actually happening is that noise is coupling through the scope from the noisy switch node. We have an article about this called "Understanding, Measuring, and Reducing Output Voltage Ripple"

    This article explains: "Another pitfall of measuring output noise is taking other measurements at the same time while measuring VOUT. For example, you may want to look at the switch waveform as you are also observing the output voltage ripple. But measuring the switch node at the same time as the output voltage will couple in additional noise and make your output voltage noise measurement worse. This is regardless of whether you use a ground wire wrapped around the probe."

    The article shows an example and explains that you can fix this issue by placing a 2k resistor in series with the SW node probe.

    -Sam